Tilting electrical melting furnace of egg shaped cross section



L. K. G. HOGL EIAL TILTING ELECTRICAL MELTING FURNACE OF EGG: SHAPED CROSS SECTION Original Filed Sept. 28, 1948 ATTOR Y ,is permissible for furnaces which,

Patented Aug. 25, 1953 o en FURNACE or EGG SHAPED caoss SECTION I Lennart K. G. Hogl and Ludwig Dreyfus, vu-

teras, Sweden, minors to Elektriska Aktieboia corporation of Swede Allmanna Svenska get, Valte Sweden, I. n

Continuation of application Serial No.

September 28, 1948. This application 51,496, October 27, 1950, Serial No. 192,441. In Sweden October 31, 1947 4 Claims.

. This application is a continuation of our application Serial No. 51,496, flied September 28, 1948, now abandoned.

The need for large high frequency furnaces especially for melting pig-iron and steel has in recent years greatly increased. However, on the one hand it is not possible to increase at will the melting-pot volume in a furnace of this type by increasing the depth of the bath, since the depth of the bath cannot be allowed to exceed a certain limited value. If this value is exceeded, due to the pressure on the bottom and the lower portion of the melting-pot under the prevailing high melting temperatures, there is risk of the meltingpot material being softened and washed oil together with the molten metal. On the other hand there is also a certain upper limit for the melting-pot diameter, which may not be exceeded. With too great a melting-pot diameter, the vault radius becomes too large, so that there is a risk that, during the tapping of the furnace, the upper portion of the melting-pot may fall or rush down.

This invention concerns an improved feature of the melting-pot adapted to reduce the aforementioned risks so that it will be possible to construct extremely large high frequency furnaces without increasing the strains on the melting-pot bottom or the melting-pot walls beyond the value which according to present working practice, can be expected to have practicable durability and life.

According to the invention the melting-pot is formed with a longitudinally extending eggshaped section, the tipping of the melting-pot being accomplished around the minor axis or around an axis parallel therewith. The tipping mouth is placed at the wider end, the narrow end thus being raised during the tapping of the furnace. By forming the melting-pot in the manner just described the portion of the melting-pot, which is raised upwards during the tipping, i. e. the melting pot wall section opposite to the tapping mouth, may be given such a small radius, that there is no risk of rushing-down during the tapping although the melting-pot volume is considerably greater than has been possible hitherto. By virtue of this invention, without exceeding the advisable depth of the bath and without any disadvantages from both the working practice and the metallurgic points of view, the volume of the melting-pot may be doubled or more than doubled as compared with furnaces hitherto constructed. In order to facilitate the manufacture of the melting-pot patterns, the egg-shaped section can 2 be constructed by means of arcs of circles with three different radii. In certain cases it may be advisable to vary the shape of the sections of the melting-pots according to the distance from the bottom of the melting-pot,

In order that the invention may be clearly understood and readily carried into effect, it will now be described more fully with reference to the drawing, wherein Figs. 1 and 2 show a vertical section and a top plan respectively of a furnace embodying the invention. Fig. 3 is a schematic verticalsection, and Fig. 4 is a plan of a modified form of the invention. Figs. 5 and 6 are a schematic vertical section and a plan respectively of another modified form of the invention. In the drawing, I designates the stamped melting-pot, the lower end of which rests on supports 2 and 3 of brickwork. The melting-pot is surrounded by a coil 4 of water-cooled copper pipe and outside this coil a number of vertically laminated sheet metal staples 5 are provided, the lower ends of which engage a ring 6 of brickwork. At the upper end the melting-pot is surrounded by a flangel. likewise of brickwork, and between this flange and the upper end of the pipe coil there is mounted a ring of heat-insulating material. The melting-pot is provided with a tapping mouth 9 and the furnace is surrounded by a sheet-metal housing In secured at its lower portion to a framework H, which supports the brick layers 2 and 6. The furnace as a whole is pivoted on a shaft It. The top of the furnace is covered by a cover plate I: extending to the melting-pot itself.

In Figs. 1 and 2, the allel vertical walls with an egg-shaped crosssection taken horizontally of the furnace when in its untilted position. As will be clear from the arrows in Fig. 2, the side walls, that is, those running generally horizontally in the drawing, are formed by arcs of circles of relatively long radius (r1, r2) The front wall adjacent the spout 9 is described by an arc of shorter radius (13) while the back wall is in the form of an arc of still shorter radius (14). Also, the pivot I2 is parallel to the minor axis of the section.

Figs. 3 and 4 show an embodiment of the invention wherein the melting chamber I has a tapering form with an egg-shaped horizontal cross-section throughout its height. Figs. 5 and 6 show another embodiment of the invention wherein the melting chamber also has a tapering form, the lower minimum cross-section being circular and changing into egg-shaped cross-sections.

melting chamber has par- We claim as our invention:

1. An electric induction melting furnace comprising a melting chamber with an internal lining of refractory material, wherein at least'the upper part of said chamber has an internal horizontal cross-section of egg shape with side walls of maximum radius of curvature, with one end of minimum radius of curvature and the opposite end of intermediate radius of curvature, an electric heating coil surrounding said chamber, and a tapping mouth located at the top of the chamber end with said intermediate radius of curvature, and the tilting axis of said chamber being so located that, when the furnace is tilted tor pouring, the end having the minimum radius of curvature is raised with respect to the end having the intermediate radius of curvature and by its relatively narrow construction resists any tendency of the refractory material to collapse.

2. An electric furnace according to claim 1, in which the areas of all the egg-shaped internal horizontal cross-sections of the melting chamber are equal.

3. An electric furnace according to claim 1, in which the areas of the egg-shaped internal horizontal cross sections of the melting chamber increase from the bottom to the top.

4. An electric furnace according to claim 1, in which the internal surface of the bottom or the said chamber is circular.

LENNART K. G. HOGEL.

LUDWIG DREYFUS.

References Cited in the file or this patent UNITED STATES PATENTS Number Name Date 663,945 Waldberger et a1. Dec. 18, 1900 1,333,950 Trembour Mar. 16, 1920 1,350,714 Foley Aug. 24, 1920 1,352,580 Cinille Sept. 14, 1920 1,411,158 Bradley et-al Mar. 28, 1922 1,439,409 Gaskill Dec. 19, 1922 1,595,970 Weed Aug. 10, 1926 1,633,876 Swigert June 28, 1927 1,681,943 Marshall Aug. 28, 1928 1,755,411 Pierce Apr. 22, 1930 1,768,881 Brace July 1, 1930 2,120,223 Wyatt June 7, 1938 2,406,147 Hopkins Aug. 20, 1946 2,556,125 Wallis June 5, 1951 

